Sort of like this (was testing the entities, manually placed):

The collision box must contain the 0,0 point (centre of entity) for some reason, so I've had to allow these things to be off-map to place them in desired locations.
Problem I'm having is that the player character seems to magically run through them. At first I thought it was just the slide distance of the character, and that does seem to be happening, but if there's a line of the entities with not enough space to squeeze through the character collision box, the character shouldn't be able to run between the entity collision boxes... but it does, giving the appearance that they're not even there.
Any ideas?